1. Field of the Invention
The present invention relates to a liquid crystal display device, and specifically to a liquid crystal display device including two liquid crystal display panels located back to back. The present invention also relates to a mobile electronic device including such a liquid crystal display device.
2. Description of the Related Art
Recently, mobile phones have been progressively spread, and foldable type phones are now mainstream. Especially, two screen type phones having a main display screen for displaying main information, and a sub display screen for displaying information in a supplementary manner where the phone is folded are popular owing to the convenience thereof. A two screen type mobile phone is described in, for example, Japanese Laid-Open Patent Publication No. 2001-136247.
FIG. 16 shows a liquid crystal display device usable for two screen type mobile phones. A liquid crystal display device 800 shown in FIG. 16 includes two liquid crystal display panels 810 and 820 located back to back. One of the liquid crystal display panels, 810, is used for a main screen (hereinafter, referred to as a “main panel”), and the other liquid crystal display panel 820 is used for a sub screen (hereinafter, referred to as a “sub panel”).
The main panel 810 includes a pair of substrates 810a and 810b, and a liquid crystal layer 812 provided therebetween. A pair of polarizing plates 801 and 802 are respectively provided outside the substrates 810a and 810b. The sub panel 820 includes a pair of substrates 820a and 820b, and a liquid crystal layer 822 provided therebetween. A pair of polarizing plates 803 and 804 are respectively provided outside the substrates 820a and 820b. 
The liquid crystal display device 800 also includes an illumination device 830 for emitting light toward the main panel 810 and an illumination device 840 for emitting light toward the sub panel 820. The illumination device 830 for the main panel 810 is an edge light type backlight including a light source 831 and a light guide plate 832 for guiding the light emitted from the light source 831 toward the main panel 810. The illumination device 840 for the sub panel 820 is also an edge light type backlight including a light source 841 and a light guide plate 842 for guiding the light emitted from the light source 841 toward the sub panel 820.
Today, mobile phones are desired to be thinner so that the user is not disturbed by the thickness thereof even in a folded state, and thus the liquid crystal display devices used for the mobile phones are also desired to be thinner.
However, the liquid crystal display device 800 shown in FIG. 16 includes two liquid crystal display panels 810 and 820 and also two illumination devices, and therefore is about twice as thick as usual liquid crystal display devices including one liquid crystal display panel.